1. Field of the Invention
This invention relates to a spindle apparatus which is particularly suitable for rotating an overhung rotor at high speed, as in a device for rotating a cutting or grinding tool at high speed, a ring spinning machine, a spinning machine, a rotor type open-end spinning machine, or a rotating spraying type coating apparatus having a bell- or disk-shaped spraying head which is rotatable at high speed. More particularly, this invention relates to a high-speed spindle having a spindle shaft which is rotatable at a high speed in a neck bearing disposed elastically in a stationary holding member and an end bearing secured thereto.
2. Description of the Prior Art
Referring by way of example to a textile machine, there is known a spindle including a casing, a neck bearing secured to the casing, an end bearing attached to the casing by a buffer, and a spindle shaft supported rotatably by the neck and end bearings and adapted to be driven by a belt extending about a pulley provided substantially at the same position as the neck bearing, as shown in, for example, Japanese Laid-Open Patent Specification No. 11914/1972 or 1230/1973. The buffer is effective for preventing vibration of the shaft and its generation of noise as long as the spindle is driven at a rotating speed up to, say, 1000 rpm. It is, however, not effective at all if the spindle is driven at a speed of, or above, say, 15,000 rpm. The vibration of the shaft and the noise thereby produced make the rotation of the spindle virtually impossible at such a high speed.
Another known apparatus is a modification to the spindle hereinabove described and has a buffer provided between the neck bearing and the casing, too, in order to overcome the drawback which has hereinabove been pointed out. This buffer is, however, not effective, either, to ensure any stable rotation of the spindle shaft at such a high speed as hereinabove mentioned, since the tension which is exerted on the neck bearing by the driving belt limits the movement of the shaft. Moreover, as the buffer and the driving pulley are both provided at the neck bearing, the apparatus has the disadvantage of requiring a larger pulley diameter to enable the location of the buffer and, therefore, a higher belt speed to maintain the same rotating speed of the spindle shaft. This undesirably brings about an increase in power consumption and a greater degree of vibration.
Referring to a tool rotating apparatus or a rotating spraying type coating apparatus, it has been conventional to employ a spindle shaft having a sufficiently large diameter to enable its critical rotating speed to exceed the working speed of the apparatus in order to realize a high speed of rotation, therefore, it has been possible to solve the problem of vibration. The spindle shaft, however, requires a bearing having a correspondingly larger outside diameter and the heat of friction generated by the bearing limits the possibility of increasing the rotating speed of the shaft. There is, therefore, known an apparatus which includes a device for the forced feed lubrication of the bearing, or an apparatus in which an air bearing is used. These apparatuses are, however, expensive and consume a larger amount of power.